Industrial activities frequently involve a need to chemically interact liquids with each other. For example, it is oftentimes necessary to combine a liquid stream with another liquid, either to synthesize a new chemical product by chemical reaction, or in some instances, to render noxious liquids substantially harmless. In still other cases, liquids are combined to achieve a physical effect, as in the case where polymeric flocculents are added to, for example, sewage wastes in the process of their treatment.
In the case of the mining industry, for instance, it is commonly necessary to chemically treat mine seepage to control pH and precipitate dissolved metals prior to discharge. In such cases, sulfur-bearing rock formations are frequently associated with the mine geology, and these are subject to leaching by acidic water seeping into the mine through the overlying strata. As a consequence, such seepage often becomes contaminated with sulfur-containing acids as it passes through sulfidebearing strata, for example, geological formations containing pyritic sulfur, making it undesirable, if not illegal to discharge the seepage wastes into the environment without first neutralizing the contaminating sulfurous materials. As indicated, these are typically acidic in nature, creating a hazard to plant and animal life with which such seepage comes in contact, either directly or indirectly.
As a consequence, and in order to comply with state and federal environmental and mining regulations, it has been become commonplace to introduce a neutralizing material, such as for instance, liquid caustic soda to such wastes to facilitate the precipitation of metals before before releasing the wastes to the environment.
One method for treating mine seepage wastes involves collecting the wastes in an intermediate storage tank prior to treatment. Thereafter, following filling of the tank to a predetermined level, a portion of the tank's contents are automatically syphoned from the tank, activating a caustic-dispensing, spring-loaded valve by impact of the syphoning stream against the valve actuating mechanism. Caustic soda introduced through the actuated valve mixes with the wastes, which then travel through an open mixing trough during a reaction process between the waste and the caustic, the neutralized stream ultimately being deposited, for instance, in a waste water storage and settling pond. While the system described can be successfully employed to treat the wastes, it has the distinct disadvantage of risking inadvertent contact of those in the vicinity of the treatment equipment with hazardous materials during the treatment process.
Another method of neutralization involves passing the acid wastes over sodium carbonate briquettes; however, this process suffers from the fact that the briquettes are somewhat hazardous materials, in addition to which, the reaction rate and the amount of treatment are difficult to control, and the operation is relatively labor intensive.